1. Field of the Invention
The present invention is directed to a method for incorporating an oil-soluble photographic additive into a hydrophilic colloid layer and, more particularly, to a method for dispersing an oil-soluble photographic additive into a hydrophilic colloid composition or into water.
2. Description of the Prior Art
In the preparation of photographic silver halide emulsion layers and hydrophilic colloid layers other than the photographic silver halide emulsion layers, either water-insoluble or slightly water-soluble materials (hereinafter referred to as "oil-soluble photographic additives") often must be incorporated therein. These additives that are insoluble in a hydrophilic colloid medium should be uniformly dispersed in a very finely divided form.
Color photographic light-sensitive materials using a variety of light-sensitive components are known, but, in general, silver halide is employed as a light-sensitive component. Such a silver halide color photographic light-sensitive material comprises a support having thereon, in sequence, a red-sensitive silver halide emulsion, a green-sensitive silver halide emulsion and blue-sensitive silver halide emulsion, in various orders. For example, a mixed grain method, a multilayer color light-sensitive material, a color diffusion transfer method, a silver dye bleach color photographic method, and many other methods are known.
In recent years, rendering a photographic additive which is to be employed in a silver halide color photographic light-sensitive material oil-soluble and dissolving such in a substantially water-insoluble high-boiling point solvent (for instance, a high-boiling point organic solvent) and then dispersing the resulting solution in a hydrophilic colloid aqueous solution generally using an anionic surface active agent as an emulsifying agent, for the purpose of various improvements in color photographic materials, has been an approach widely employed in the photograhic art.
Examples of oil-soluble photographic additives include an oil-soluble coupler, an ultraviolet absorbant, an anti-color fading agent, an antioxidant, a dye releasing agent for the color diffusion transfer method, a dye developer, and many other additives.
Numerous methods for emulsion dispersing such oil-soluble photographic additives, for example, as described in U.S. Pat. Nos. 2,739,888, 3,352,681, etc., relating to ultraviolet light absorbants; U.S. Pat. Nos. 2,360,290, 2,728,659, 3,700,453, etc., regarding diffusion resistant alkyl hydroquinones which are employed for preventing color fog, color stain, color mixing, etc., are known. In particular, methods for emulsion dispersing oil-soluble photographic additives in which anionic surface active agents are employed as emulsifying agents are known. For example, a method using Gardinol WA (trade name for a sulfonated coconut fatty alcohol, made by E. I. Du Pont de Nemours Co., Inc.) and triisopropyl naphthalenesulfonic acid salt as described in U.S. Pat. No. 2,332,027; a method using as an emulsifying agent a water-soluble coupler having a sulfo group or carboxyl group and a long chain aliphatic group in combination as described in Japanese Pat. No. 428,191; and a method using an anionic surface active agent having a sulfo group in combination with an anhydrohexyl ester type nonionic surface active agent as described in U.S. Pat. No. 3,676,141 are known. All of these emulsion dispersing methods provide coarse dispersion particles (e.g., a particle size larger than about 2.mu.) and do not result in finely divided dispersion particles (e.g., smaller than about 0.5.mu.), which have been required in recent photographic light-sensitive materials, being produced. In particular, the thickness of photographic elements to be coated onto a support in design of color photographic light-sensitive materials have increased and, therefore, if a dispersion to be incorporated therein is composed of coarse particles, light scattering which adversely affects the photographic properties occurs, when light passes through a photographic element, and this results in turbidity. In addition, light scattering also deteriorates the image quality such as image sharpness, graininess or the like. On the other hand, particularly, if microparticles of a coupler dispersion are formed, the surface area per unit weight of the particles becomes large, color formation speed as well as efficiency are increased, the covering power of the dye images formed is also increased, and the image density increases. However, generally, a large amount of an emulsifier must be used in order to markedly decrease the particles of a dispersion. If a large amount of an emulsifier is employed, coating difficulties due to foaming of an emulsion, for example, occurrence of pin holes, uneven thickness in the coated layers, etc., tend to occur. In addition, a deterioration in the film quality of a photographic element in which light-sensitive materials are coated (for example, the tackiness and adhesivity of the coated layers increase especially at high temperature and high humidity so that undesired adhesion between photographic light-sensitive materials or between the material and a camera, etc., tends to occur) results. Furthermore, a prevention of the antistatic effects due to an antistatic agent which may be employed in combination is also encountered. If the particle size of dispersed particles of an emulsion dispersion is further decreased, aggregation of particles, a destruction of the dispersion, etc., tend to occur with the passage of time, in general.
With the use of the above-described conventional surface active agents, formation of a finer dispersion cannot be achieved without the defects accompanying such finer particles being encountered.